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Nwabuobi et al. Thymoma associated panencephalitis

bilateral lung apices. This mass was later confirmed to drastic improvement in his clinical symptoms with
be a metastatic type B2, stage III thymoma via biopsy just immunotherapy, unlike other cases that showed
and after resection [Figure 2]. The patient was treated improvement after thymomectomy and/or extensive
with intravenous methylprednisolone (1 g/day for 10 immunotherapy. In order to further characterize TAPE
days) followed by 0.4 g/kg daily immunoglobulin (IVIG) as a paraneoplastic syndrome, antibody associations
for total of 4 days. He had significant improvement in need to be elicited.
his mental status with the first dose of steroids. Repeat
imaging 2 weeks after initial presentation showed In reviewing the prior reported cases, these patients
improvement in the cortical lesions, specifically, can have a variety of autoantibodies as seen in
decrease in the abnormal fluid-attenuated inversion Table 1, the most common being AchR, present in 9
recovery (FLAIR) hyperintensities [Figure 1]. Further of 16 cases, with 5 having symptoms of myasthenia
treatment included chemotherapy with cisplatin, gravis (MG). This is not surprising as up to 37% of
doxorubicin, and cyclophosphamide given the invasive patients with thymic tumors but without MG have been
nature of the thymoma. Prior to thymomectomy, his reported to have positive antibody titers to AchR.
[5]
course was complicated by gastrointestinal dysmotility Voltage-gated potassium channel (VGKC) was the 2nd
syndrome thought to be a result of his paraneoplastic most common antibody seen in 5 patients. It has been
syndrome. He underwent a successful thymomectomy proven that the antibodies to VGKC actually target
with complete resection approximately 3 months the associated proteins LGI1 and Caspr2, and not the
after initial presentation, and continued to improve channel itself, therefore rendering the term, “antibodies
thereafter. to VGKC” obsolete. Antibodies to LGI1 and Caspr2
[6]
were present in 3 and 1 of the patients, respectively.
DISCUSSION Both CRMP-5 and GAD were occasionally present
among the cases. The presence of GAD antibodies
Based on literature review, our patient is one of the in thymoma is associated with stiff person syndrome
[1]
very few reported cases of thymoma-associated and unlikely to manifest as encephalitis. CRMP-5
panencephalitis (TAPE). These cases highlight the has been shown to be a marker of immune response
similar neurological symptoms at presentation -- initiated by thymomas in different PNS, and therefore,
seizures, confusion, and memory loss being the most may not be neuropathogenic. Antibodies against
[7]
common -- with a constellation of positive antibodies Hu, Ri, and Yo were the least common, absent in
and different responses to treatment [Table 1]. The 50% of the patients. Review of associated antibodies
similar presentations and MRI findings in these in these previously reported cases does not show a
patients support TAPE as a distinct disease entity clear pattern, and it is unclear which antibodies are
and autoimmune disorder. Our case was unique actually pathologic and which ones are incidental. Of
as our patient was found to have multiple neuronal significant importance, Petit-Pedrol et al. recently
[8]
and non-neuronal antibody responses and had a reported 6 patients who presented very similarly to

Figure 2: Computed tomography chest showing large right mediastinal mass. Contrast-enhanced computed tomography images (A:
axial; B: coronal), showing a large multilobulated right anterior mediastinal mass measuring 6.0 cm × 4.7 cm in transverse dimension by
approximately 13 cm in craniocaudal dimension. There was found to be mass effect with mild compression of the right atrium and superior
vena cava (though patent). Thymoma was suspected, and proven later on biopsy
Neuroimmunology and Neuroinflammation ¦ Volume 4 ¦ June 16, 2017 119